In recent years, there has been an increasing demand for infrared detectors for the purpose of executing thermal detection or measuring concentrations of carbon dioxide or air pollutants. There are a plurality of candidates for materials and structures of infrared detectors, and one of them is a Quantum Dot Infrared Photodetector (hereinafter referred to as “QDIP”) in which semiconductor quantum dots are included in a light-absorbing layer.
The QDIP has a structure in which quantum dots are surrounded three-dimensionally by a semiconductor having a bandgap larger than that of materials forming the quantum dots. Further, electrons and holes are strongly confined in the quantum dots. As a result, discrete energy levels are formed in the quantum dots. Among these levels, a plurality of electron subband levels in a conduction band may be used to detect infrared light having energy corresponding to the difference in energy between subbands.
Patent Literature 1 discloses a photodetector capable of easily reducing a dark current to improve the performance of the detector.
Patent Literature 2 discloses an optical semiconductor device that can be easily manufactured and can sufficiently suppress a dark current and achieve optical detection with high sensitivity.
Patent Literature 3 discloses a quantum dot infrared detector having excellent properties because it achieves both easily growing of crystals forming a current block layer and a high potential barrier with respect to a dark current.